Welding A286 to Inconel 718

[kevlar49]

I am trying to TIG tack weld A286 to Inconel 718 and have a 0.015” gap between the parts. There are two tacks and usually it is the second tack 180 degrees apart that cracks, although occasionally both tacks will crack. I have tried welding with Hastelloy W and Haynes 556. I am wondering if Hastelloy C-276 will work better than either of those two rods because it contains much lower B, C, and Zr. The tack welds are only exposed to air, not a corrosive environment.

Does anyone have experience with this combination? Does anyone have experience to say whether the C-276 rod would help or hurt?

 

[metengr]

Where exactly are the cracks observed - in the center of the tack weld or along the Inconel 718 side of the tack weld?

 

[kevlar49]

Center at emanating from root. Not on the 718 side.

 

[metengr]

Use Hastelloy S (AMS 5838), this is formulated for DMW of 718 to other alloys. Try using a larger width to depth ratio for the tack weld.

 

[EdStainless]

And try three welds. Putting two right across from each other really jacks the stress levels up. These alloys have significant thermal expansion.

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Plymouth Tube

 

[kevlar49]

All,
did the other combination Hastelloy W or Haynes 556 seem to have hot short problems with them.

Metengr, I noticed here:
that Hastelloy S has 0.015 boron. Is this an error? I have an ASM desk reference that says that there is La but no B. Is that still going to raise some hot shortness concerns? It has more boron than A286 (0.005 max)

Edstainless, did you mean one butter on inconel 718, one on A286, and finally one to join the two butters together?

 

[metengr]

kevlar49
No, I did not see hot cracking as being an issue with the other two selections. Typically, joint restraint, weld profile and hot filler metal strength have more to do with centerline cracking for these types of tack welds. The source I have from Haynes lists B content as 0.015 maximum percent by mass. The La content is fixed at 0.02 percent by mass.

 

[kevlar49]

Edstainless,

did you mean putting 3 at 60 degrees apart from each other?

 

[EdStainless]

I was thinking 3 x 120 deg
If you don't need the hot strength why not use 82 as a filler?
Better ductility and easy to weld.

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Plymouth Tube

 

[kevlar49]

EdStainless,

Sorry, meant 120 deg. Someone just suggested it. Hadn't crossed my mind at the time. Looking into it now. Someone also suggested 725NDUR. Any experience with that? By the way, the tack is used as a substitute for a thread locking compound, there will not be a full joint weld.

 

[metengr]

Inco 82 might be an easier alternative. I don't see any issues with the A-286 base material.